U.S. patent application number 14/377174 was filed with the patent office on 2014-12-18 for display element.
The applicant listed for this patent is Sharp Kabushiki Kaisha. Invention is credited to Tomoko Nango, Satoshi Shibata, Yuka Utsumi, Makoto Yamada.
Application Number | 20140368766 14/377174 |
Document ID | / |
Family ID | 48947417 |
Filed Date | 2014-12-18 |
United States Patent
Application |
20140368766 |
Kind Code |
A1 |
Shibata; Satoshi ; et
al. |
December 18, 2014 |
DISPLAY ELEMENT
Abstract
A display element includes: a light source; a phosphor layer
configured to absorb light from the light source as excitation
light and generate light in a wavelength region different from a
wavelength region of the light source; a functional optical film
configured to reflect the light emitted from the phosphor layer;
and a light extraction structure having a function of emitting the
light emitted from the phosphor layer to a non-light source,
wherein the functional optical film is a band pass filter formed of
a dielectric multilayer film, and a low refractive index layer is
provided between the phosphor layer and the band pass filter, the
low refractive index layer having a refractive index lower than
those of the phosphor layer and a medium of band pass filter.
Inventors: |
Shibata; Satoshi; (Osaka,
JP) ; Nango; Tomoko; (Osaka, JP) ; Yamada;
Makoto; (Osaka, JP) ; Utsumi; Yuka; (Osaka,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sharp Kabushiki Kaisha |
Osaka-shi |
|
JP |
|
|
Family ID: |
48947417 |
Appl. No.: |
14/377174 |
Filed: |
February 1, 2013 |
PCT Filed: |
February 1, 2013 |
PCT NO: |
PCT/JP2013/052367 |
371 Date: |
August 6, 2014 |
Current U.S.
Class: |
349/61 ;
362/84 |
Current CPC
Class: |
G02F 1/1339 20130101;
G02F 2001/133521 20130101; G02F 1/133617 20130101; G02F 1/133514
20130101; F21V 9/08 20130101; G02F 1/133553 20130101; G02F 1/133509
20130101; G02B 5/285 20130101; G02B 5/201 20130101; H01L 27/322
20130101 |
Class at
Publication: |
349/61 ;
362/84 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335; F21V 9/08 20060101 F21V009/08; G02F 1/1339 20060101
G02F001/1339 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 7, 2012 |
JP |
2012-024170 |
Claims
1. A display element comprising: a light source; a phosphor layer
configured to absorb light from the light source as excitation
light and generate light in a wavelength region different from a
wavelength region of the light source; a functional optical film
configured to reflect the light emitted from the phosphor layer;
and a light extraction structure having a function of emitting the
light emitted from the phosphor layer to a non-light source,
wherein the functional optical film is a band pass filter formed of
a dielectric multilayer film, and a low refractive index layer is
provided between the phosphor layer and the band pass filter.
2. The display element according to claim 1, wherein the light
source has at least one maximum value in a range of wavelengths
from 400 nm to 490 nm in an emission spectrum, and the functional
optical film is a band pass filter including a dielectric
multilayer film, having a region showing maximum transmittance in
the range of wavelengths from 400 nm to 490 nm within a
transmission spectrum and having a reflection band in a region of
longer wavelengths than a wavelength of 490 nm.
3. The display element according to claim 1, wherein the low
refractive index layer is an air layer.
4. The display element according to claim 1, wherein the low
refractive index layer is a resin layer.
5. A display element comprising: a light source; a light control
element configured to control an amount of light from the light
source; a phosphor layer configured to absorb the light transmitted
through the light control element as excitation light, and generate
light in a wavelength region different from a wavelength region of
the light source; a functional optical film configured to reflect
the light emitted from the phosphor layer; and a light extraction
structure having a function of emitting the light emitted from the
phosphor layer to a non-light source, wherein the light source has
at least one maximum value in a range of wavelengths from 400 nm to
490 nm within an emission spectrum, and the light control element
is a liquid crystal element interposed between a pair of
polarization plates, and the functional optical film is a band pass
filter including a dielectric multilayer film, having a region
showing maximum transmittance in the range of wavelengths from 400
nm to 490 nm within a transmission spectrum, and having a
reflection band in a region of longer wavelengths than a wavelength
of 490 nm.
6. The display element according to claim 1, wherein the light
extraction structure protrudes to one surface of the phosphor layer
and comes in contact with one surface of the band pass filter, and
the low refractive index layer arranged between the phosphor layer
and the band pass filter is sealed in a periphery.
7. The display element according to claim 1, wherein the light
extraction structure protrudes to one surface of the phosphor layer
and comes in contact with one surface of the band pass filter, and
the low refractive index layer arranged between the phosphor layer
and the band pass filter includes an opening in a periphery.
8. The display element according to claim 1, wherein the light
extraction structure includes an adhesive layer protruding to the
one surface of the phosphor layer and comes in contact with one
surface of the band pass filter, and the low refractive index layer
arranged between the phosphor layer and the band pass filter is
sealed in a periphery.
9. The display element according to claim 1, wherein the low
refractive index layer and the band pass filter are interposed
between the one surface of the first substrate on which the
phosphor layer is formed and one surface of the second substrate
supporting the light control element, and the surfaces are bonded
with a sealing material.
10. The display element according to claim 1, wherein the low
refractive index layer and the band pass filter are interposed
between one surface of the first substrate on which the phosphor
layer is formed and one surface of the second substrate supporting
the light control element, the surfaces are bonded with a sealing
material, and a periphery of the phosphor layer and a periphery of
the band pass filter have a gap with the sealing material.
11. The display element according to claim 1, wherein the phosphor
layer, the low refractive index layer and the band pass filter are
interposed and arranged between one surface on the light source
side of the substrate on the non-light source side of the light
control element interposed and arranged between a pair of
substrates and a polarization plate on the non-light source side of
the light control element.
12. The display element according to claim 1, wherein the phosphor
layer, the low refractive index layer and the band pass filter are
interposed and arranged between one surface on the light source
side of the substrate on the non-light source side of the light
control element interposed and arranged between a pair of
substrates and a polarization plate on the non-light source side of
the light control element, and one surface of the substrate on the
non-light source side on which the phosphor layer is formed and one
surface of the substrate on the light source supporting the light
control element are adhered with a sealing material.
13. The display element according to claim 1, wherein the phosphor
layer, the low refractive index layer and the band pass filter are
interposed and arranged between one surface on the light source
side of the substrate on the non-light source side of the light
control element interposed and arranged between a pair of
substrates and a polarization plate on the non-light source side of
the light control element, one surface of the substrate on the
non-light source side on which the phosphor layer is formed and one
surface of the substrate on the light source supporting the light
control element are adhered with a sealing material, and a
periphery of the phosphor layer and a periphery of the band pass
filter have a gap with the sealing material.
14. The display element according to claim 5, wherein the
functional optical film is a band pass filter including a
dielectric multilayer film, having a region showing maximum
transmittance in the range of wavelengths from 400 nm to 490 nm
within a transmission spectrum, having a reflection band in a
region of longer wavelengths than a wavelength of 490 nm, and
reflecting light between 490 nm and 1000 nm for light at an
incidence angle 0.degree..
15. A display element comprising: a light source; a light control
element configured to control an amount of light from the light
source; a phosphor layer configured to absorb the light transmitted
through the light control element as excitation light, and generate
light in a wavelength region different from a wavelength region of
the light source; a functional optical film configured to reflect
the light emitted from the phosphor layer; and a light extraction
structure having a function of emitting the light emitted from the
phosphor layer to a non-light source, wherein the functional
optical film is a band pass filter including a dielectric
multilayer film, having a region showing maximum transmittance in
the range of wavelengths from 400 nm to 490 nm within a
transmission spectrum and having a reflection band in a region of
longer wavelengths than a wavelength of 490 nm, and the light
control element includes an MEMS.
16. (canceled)
17. The display element according to claim 1, wherein the band pass
filter is a dielectric multilayer film using an organic film.
18. The display element according to claim 1, wherein the band pass
filter includes the low refractive index layer and the dielectric
multilayer film that are formed integrally, the low refractive
index layer has a refractive index lower than any of a high
refractive index layer and a low refractive index layer
constituting the dielectric multilayer film, and a film thickness
of the low refractive index layer is greater than a wavelength of a
visible light region.
19. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to a display element, and an
illumination device including this display element.
[0002] Priority is claimed on Japanese Patent Application No.
2012-024170, filed on Feb. 7, 2012, the content of which is
incorporated herein by reference.
BACKGROUND ART
[0003] There are display elements in which excitation light emitted
from a light source is color-converted by a phosphor layer and
emitted to an observer. As such display elements, a display element
in which blue excitation light emitted from a backlight unit and
modulated by a liquid crystal panel is color-converted by a red
phosphor layer, a green phosphor layer and a blue color filter, and
full-color display is performed, and a display element in which
light from a light emitting layer arranged between a pair of
electrodes is converted into a guided light wave component using a
low refractive index layer and scattered by a nano structure layer,
and light extraction to an observer is performed are known (Patent
Document 1).
[0004] Further, for example, a display element in which a light
reflection film is provided is known as a display element for
enhancing efficiency of the light extraction to the observer
(Patent Document 2). The light reflection film includes, for
example, a silicon oxide film, a niobium oxide film, and a
multilayer laminated film formed of a low refractive index material
and a high refractive index material (e.g., a multilayer laminated
film including a silicon oxide film and a niobium oxide film).
PRIOR ART DOCUMENTS
Patent Document
[Patent Document 1] Japanese Unexamined Patent Application, First
Publication No. 2005-251488
[Patent Document 2] Japanese Unexamined Patent Application, First
Publication No. 2009-134275
SUMMARY OF INVENTION
Problem to Be Solved by the Invention
[0005] The display element using color conversion of the phosphor
layer has a problem in that, since the phosphor layer emits light
isotropically within the display element, there is a light
component that is confined due to a light guiding effect by total
reflection and particularly, extraction to the observer of light
emitted in a back direction of the observer side is difficult and
not efficiently used as display light.
[0006] The present invention has been made in view of the
circumstances described above, and an object of the present
invention is to provide a display element and an illumination
device in which light emitted isotropically from a phosphor layer
can be efficiently extracted.
Means to Solve the Problem
[0007] To solve the technical problem, a display element according
to one embodiment of the present invention includes:
[0008] a light source;
[0009] a phosphor layer configured to absorb light from the light
source as excitation light and generate light in a wavelength
region different from a wavelength region of the light source;
[0010] a functional optical film configured to reflect the light
emitted from the phosphor layer; and
[0011] a light extraction structure having a function of emitting
the light emitted from the phosphor layer to a non-light
source,
[0012] wherein the functional optical film is a band pass filter
formed of a dielectric multilayer film, and a low refractive index
layer is provided between the phosphor layer and the band pass
filter.
[0013] The light source may have at least one maximum value in a
range of wavelengths from 400 nm to 490 nm in an emission spectrum,
and
[0014] the functional optical film may be a band pass filter
including a dielectric multilayer film, having a region showing
maximum transmittance in the range of wavelengths from 400 nm to
490 nm within a transmission spectrum and having a reflection band
in a region of longer wavelengths than a wavelength of 490 nm.
[0015] The low refractive index layer may be an air layer.
[0016] The low refractive index layer may be a resin layer.
[0017] In addition, a display element according to one embodiment
of the present invention includes:
[0018] a light source;
[0019] a light control element configured to control an amount of
light from the light source;
[0020] a phosphor layer configured to absorb the light transmitted
through the light control element as excitation light, and generate
light in a wavelength region different from a wavelength region of
the light source;
[0021] a functional optical film configured to reflect the light
emitted from the phosphor layer; and
[0022] a light extraction structure having a function of emitting
the light emitted from the phosphor layer to a non-light
source,
[0023] wherein the light source has at least one maximum value in a
range of wavelengths from 400 nm to 490 nm within an emission
spectrum, and the light control element is a liquid crystal element
interposed between a pair of polarization plates, and
[0024] the functional optical film is a band pass filter including
a dielectric multilayer film, having a region showing maximum
transmittance in the range of wavelengths from 400 nm to 490 nm
within a transmission spectrum, and having a reflection band in a
region of longer wavelengths than a wavelength of 490 nm.
[0025] The light extraction structure may protrudes to one surface
of the phosphor layer and comes in contact with one surface of the
band pass filter, and the low refractive index layer arranged
between the phosphor layer and the band pass filter may be sealed
in a periphery.
[0026] The light extraction structure may protrude to one surface
of the phosphor layer and comes in contact with one surface of the
band pass filter, and the low refractive index layer arranged
between the phosphor layer and the band pass filter may include an
opening in a periphery.
[0027] The light extraction structure may include an adhesive layer
protruding to the one surface of the phosphor layer and comes in
contact with one surface of the band pass filter, and the low
refractive index layer arranged between the phosphor layer and the
band pass filter may be sealed in a periphery.
[0028] The low refractive index layer and the band pass filter may
be interposed between the one surface of the first substrate on
which the phosphor layer is formed and one surface of the second
substrate supporting the light control element, and the surfaces
are bonded with a sealing material.
[0029] The low refractive index layer and the band pass filter may
be interposed between one surface of the first substrate on which
the phosphor layer is formed and one surface of the second
substrate supporting the light control element, the surfaces may be
bonded with a sealing material, and a periphery of the phosphor
layer and a periphery of the band pass filter may have a gap with
the sealing material.
[0030] The phosphor layer, the low refractive index layer and the
band pass filter may be interposed and arranged between one surface
on the light source side of the substrate on the non-light source
side of the light control element interposed and arranged between a
pair of substrates and a polarization plate on the non-light source
side of the light control element.
[0031] The phosphor layer, the low refractive index layer and the
band pass filter may be interposed and arranged between one surface
on the light source side of the substrate on the non-light source
side of the light control element interposed and arranged between a
pair of substrates and a polarization plate on the non-light source
side of the light control element, and
[0032] one surface of the substrate on the non-light source side on
which the phosphor layer is formed and one surface of the substrate
on the light source supporting the light control element may be
adhered with a sealing material.
[0033] The phosphor layer, the low refractive index layer and the
band pass filter may be interposed and arranged between one surface
on the light source side of the substrate on the non-light source
side of the light control element interposed and arranged between a
pair of substrates and a polarization plate on the non-light source
side of the light control element,
[0034] one surface of the substrate on the non-light source side on
which the phosphor layer is formed and one surface of the substrate
on the light source supporting the light control element may be
adhered with a sealing material, and
[0035] a periphery of the phosphor layer and a periphery of the
band pass filter may have a gap with the sealing material.
[0036] In the band pass filter, a short wavelength end of a
reflection band may be a short wavelength side compared to a
wavelength of 490 nm for incident light at an incident angle
0.degree. from the low refractive index layer, and a long wave
length side of the refraction band may be a long wavelength side
compared to a wavelength of 750 nm for the incident light at a
maximum incident angle from the low refractive index layer. It is
preferable that the long wavelength end of the refraction band is
at long wavelength side compared to 1000 nm.
[0037] In addition, a display element according to one embodiment
of the present invention includes:
[0038] a light source;
[0039] a light control element configured to control an amount of
light from the light source;
[0040] a phosphor layer configured to absorb the light transmitted
through the light control element as excitation light, and generate
light in a wavelength region different from a wavelength region of
the light source;
[0041] a functional optical film configured to reflect the light
emitted from the phosphor layer; and
[0042] a light extraction structure having a function of emitting
the light emitted from the phosphor layer to a non-light
source,
[0043] wherein the functional optical film is a band pass filter
including a dielectric multilayer film, having a region showing
maximum transmittance in the range of wavelengths from 400 nm to
490 nm within a transmission spectrum and having a reflection band
in a region of longer wavelengths than a wavelength of 490 nm,
and
[0044] the light control element includes an MEMS.
[0045] In addition, a display element according to one embodiment
of the present invention includes:
[0046] a light source;
[0047] a light control element configured to control an amount of
light from the light source;
[0048] a phosphor layer configured to absorb the light transmitted
through the light control element as excitation light, and generate
light in a wavelength region different from a wavelength region of
the light source;
[0049] a functional optical film configured to reflect the light
emitted from the phosphor layer; and
[0050] a light extraction structure having a function of emitting
the light emitted from the phosphor layer to a non-light
source,
[0051] wherein the functional optical film is a band pass filter
including a dielectric multilayer film, having a region showing
maximum transmittance in the range of wavelengths from 400 nm to
490 nm within a transmission spectrum, and having a reflection band
in a region of longer wavelengths than a wavelength of 490 nm,
and
[0052] the light source and the light control element are blue
light emitting EL elements.
[0053] The band pass filter may be a dielectric multilayer film
using an organic film.
[0054] The band pass filter may include the low refractive index
layer and the dielectric multilayer film that are formed
integrally,
[0055] the low refractive index layer has a refractive index lower
than any of a high refractive index layer and a low refractive
index layer constituting the dielectric multilayer film, and
[0056] a film thickness of the low refractive index layer is
greater than a wavelength of a visible light region.
[0057] An illumination device according to one embodiment of the
present invention includes one of the above-described display
elements.
EFFECT OF THE INVENTION
[0058] According to the present invention, it is possible to
provide a display element and an illumination device in which light
emitted isotropically from the phosphor layer can be efficiently
extracted to an observer.
BRIEF DESCRIPTION OF DRAWINGS
[0059] FIG. 1 is a schematic cross-sectional view illustrating a
display element of a first embodiment of the present invention.
[0060] FIG. 2 is a schematic cross-sectional view illustrating
primary portions of the display element of the first embodiment of
the present invention.
[0061] FIG. 3A is a diagram illustrating reflectance due to an
incident angle at each wavelength of incident light.
[0062] FIG. 3B is a diagram illustrating incidence angle dependence
of a reflection characteristic of a band pass filter according to
the embodiment of the present invention.
[0063] FIG. 4 is a schematic view illustrating reflection of
excitation light in the first embodiment of the present
invention.
[0064] FIG. 5A is a schematic cross-sectional view illustrating a
bonding method for the display element of the first embodiment of
the present invention.
[0065] FIG. 5B is a schematic cross-sectional view illustrating a
bonded configuration of the primary portions of the display element
of the first embodiment of the present invention.
[0066] FIG. 6A is a schematic view illustrating a peripheral
sealing portion of the display element of the first embodiment of
the present invention.
[0067] FIG. 6B is a schematic enlarged view of the peripheral
sealing portion of the display element of the first embodiment of
the present invention.
[0068] FIG. 6C is a schematic view illustrating a peripheral
sealing portion of the display element of the first embodiment of
the present invention.
[0069] FIG. 7 is a schematic cross-sectional view illustrating a
variant of the display element of the first embodiment of the
present invention.
[0070] FIG. 8A is a schematic cross-sectional view illustrating a
method of bonding primary portions of a display element of a second
embodiment of the present invention.
[0071] FIG. 8B is a schematic cross-sectional view illustrating a
bonded configuration of the primary portions of the display element
of the second embodiment of the present invention.
[0072] FIG. 9 is a schematic cross-sectional view illustrating a
display element of a third embodiment of the present invention.
[0073] FIG. 10 is a schematic cross-sectional view illustrating a
display element of a fourth embodiment of the present
invention.
[0074] FIG. 11 is a schematic cross-sectional view illustrating a
display element of a fifth embodiment of the present invention.
[0075] FIG. 12 is a schematic cross-sectional view of a blue light
emitting EL element that is an example of an optical modulation
portion.
[0076] FIG. 13 is a schematic cross-sectional view illustrating a
display element of a comparative example.
[0077] FIG. 14A is a graph showing dependence of an angle of
incidence on the band pass filter of a reflection spectrum.
[0078] FIG. 14B is a graph showing dependence of an angle of
incidence on the band pass filter of a reflection spectrum.
[0079] FIG. 15 is a schematic cross-sectional view illustrating a
display element of a variant of the third embodiment of the present
invention.
[0080] FIG. 16A is a schematic cross-sectional view illustrating an
example of the illumination device of the present invention.
[0081] FIG. 16B is a schematic cross-sectional view illustrating an
example of the illumination device of the present invention.
EMBODIMENT FOR CARRYING OUT THE INVENTION
[0082] While the present invention will be described in connection
with embodiments and examples in greater detail with reference to
the drawings, the present invention is not limited to these
embodiments and examples.
[0083] In addition, it should be noted that, in a description using
the following drawings, the drawings are schematic and a ratio or
the like of each dimension is different from a real one.
Illustration of members other than members necessary for ease of
understanding is appropriately omitted. In addition, refraction at
an interface with a different refractive index is omitted in the
drawings illustrated in each of the following embodiments, and only
behavior of the transmission or reflection is illustrated.
First Embodiment
[0084] (1) Entire Configuration of a Display Element
[0085] Hereinafter, a first embodiment will be described using
FIGS. 1 to 7 and 13. FIG. 1 is a schematic cross-sectional view
illustrating a display element of this embodiment, and FIG. 13 is a
schematic cross-sectional view illustrating a display element of a
comparative example.
[0086] The display element 1 of this embodiment includes an optical
modulation portion 2, a substrate 3 arranged opposite to the
optical modulation portion 2, a phosphor layer 4 arranged on the
optical modulation portion 2 side of the substrate 3, a color
filter layer 11 arranged between the substrate 3 and the phosphor
layer 4, and a band pass filter 6 arranged with a low refractive
index layer 5 interposed between the optical modulation portion 2
and the phosphor layer 4, as illustrated in FIG. 1. In the display
element 1 of this embodiment, a red subpixel 8R that performs
display by red light, a green subpixel 8G that performs display by
green light, and a blue subpixel 8B that performs display by blue
light are arranged to be adjacent. The three subpixels 8R, 8G and
8B constitute one pixel that is a minimum unit constituting a
display.
[0087] The optical modulation portion 2 includes a backlight (light
source) 10 and a liquid crystal panel 20 (liquid crystal element).
In this embodiment, an optical modulation element includes the
liquid crystal panel 20 that can adjust optical transmittance in
each predetermined region through application of a voltage.
[0088] (1.1) Configuration of the Backlight
[0089] The backlight 10 emits excitation light L1 for exciting the
phosphor layers 4R, 4G and 4B. In this embodiment, the backlight 10
emits ultraviolet light or blue light as the excitation light L1. A
backlight having at least one maximum value in a range of
wavelengths from 350 nm to 470 nm in an emission spectrum, that is,
a backlight showing maximum intensity in the range of wavelengths
from 350 nm to 470 nm, is used as the backlight 10. Preferably, a
backlight showing maximum intensity in the range of wavelengths
from 430 nm to 470 nm is used. For example, a blue light emitting
diode (blue LED) having a maximum value around a wavelength of 450
nm is used as the backlight 10.
[0090] (1.2) Configuration of the Liquid Crystal Panel
[0091] The liquid crystal panel 20 modulates transmittance of the
excitation light L1 emitted from the backlight 10 for each of the
subpixels 8R, 8G and 8B described above. The excitation light L1
modulated by the liquid crystal panel 20 is incident on the
phosphor layers 4R, 4G and 4B. Accordingly, light emitted through
excitation of the phosphor layers 4R, 4G and 4B is emitted to the
outside. Therefore, in this embodiment, an upper side of the
display element 1 illustrated in FIG. 1 is a viewing side from
which an observer views the display.
[0092] The liquid crystal panel 20 includes a first polarization
plate 21, a first substrate 22, a liquid crystal layer 24
interposed between a pair of transparent electrodes 23 and 25, a
second substrate 26, and a second polarization plate 27, and has a
structure in which these are laminated sequentially from the
backlight 10 side. In addition, a configuration in which the second
substrate 26 is not included may be adopted as the liquid crystal
panel. In this case, a polarization plate having a sheet shape (a
polarization layer) is used as the second polarization plate 27
instead of a polarization plate having a plate shape.
[0093] The first transparent electrode 23 is formed on an inner
surface (a surface on the liquid crystal layer 24 side) of the
first substrate 22 for each subpixel, and an orientation film (not
illustrated) is formed to cover the first transparent electrode 23.
The first polarization plate 21 is provided on an external surface
(a surface opposite to the liquid crystal layer 24 side) of the
first substrate 22. A substrate formed of glass, quartz, plastic or
the like that is able to transmit the excitation light, for
example, may be used as the first substrate 22. A transparent
conductive material such as indium tin oxide (hereinafter
abbreviated as ITO), for example, is used for the first transparent
electrode 23.
[0094] A general polarization plate used for a conventional liquid
crystal display element may be used for the first polarization
plate 21.
[0095] On the other hand, the second transparent electrode 25 and
an orientation film (not illustrated) are laminated on an inner
surface (a surface on the liquid crystal layer 24 side) of the
second substrate 26. The second polarization plate 27 is provided
on an outer surface (a surface opposite to the liquid crystal layer
24 side) of the second substrate 26. A substrate formed of glass,
quartz, plastic or the like that is able to transmit the excitation
light may be used for the second substrate 26, like the first
substrate 22. A transparent conductive material such as ITO is used
for the second transparent electrode 25, like the first transparent
electrode 23.
[0096] A system for the liquid crystal panel 20 is not particularly
limited and, for example, an active matrix system in which a
switching element such as a thin film transistor (hereinafter
abbreviated as TFT) is included for each subpixel may be adopted or
a passive matrix system in which no TFT is included may be adopted.
In addition, a mode of the liquid crystal layer 24 is not
particularly limited, and various liquid crystal modes such as a TN
(Twisted Nematic) mode, a VA (Vertical Alignment) mode, and an IPS
(In-Plane Switching) mode may be adopted.
[0097] (1.3) Configuration on the Inner Surface Side of the
Substrate
[0098] A color filter layer 11, a phosphor layer 4, a low
refractive index layer 5, and a band pass filter 6 are laminated on
an inner surface (a surface on the backlight 10 side) of the
substrate 3 in this order from the substrate 3 side.
[0099] The color filter layer 11 includes a color filter layer 11R
that transmits red light, a color filter layer 11G that transmits
green light, and a color filter layer 11B that transmits blue
light. The color filter layer 11R transmitting the red light is
arranged on the phosphor layer 4R emitting the red light. The color
filter layer 11G transmitting the green light is arranged on the
phosphor layer 4G emitting the green light. The color filter layer
11 B transmitting the blue light is arranged on a light diffusion
layer that diffuses the blue light from the phosphor layer 4B
emitting the blue light or the backlight 10.
[0100] In addition, a light transmission spectrum of the color
filter layer 11 in each of RGB areas can be appropriately designed
in consideration of correction of color purity and a function as an
external light absorption filter. In addition, the color filter
layer functions as an external light cut filter. When external
light is directly incident on the phosphor layer, the phosphor is
excited, generating an unnecessary emitted light component and
causing contrast degradation. Accordingly, the external light can
be cut by the color filter layer to prevent the contrast
degradation.
[0101] A phosphor material constituting the phosphor layer 4 has a
different emission wavelength band for each subpixel.
[0102] When the excitation light from the backlight 10 is
ultraviolet light, the phosphor layer 4R formed of a phosphor
material that absorbs the ultraviolet light and emits the red light
is provided in the red subpixel 8R, the phosphor layer 4G formed of
a phosphor material that absorbs the ultraviolet light and emits
the green light is provided in the green subpixel 8G, and the
phosphor layer 4B formed of a phosphor material that absorbs the
ultraviolet light and emits the blue light is provided in the blue
subpixel 8B.
[0103] Or, when the excitation light from the backlight 10 is blue
light, phosphor layers formed of phosphor materials that absorb the
blue light and emit the red light and the green light are provided
in the red subpixel 8R and the green subpixel 8G, respectively, and
a light diffusion layer that diffuses the blue light that is
excitation light without wavelength-converting the blue light and
emits the blue light to the outside is provided in the blue
subpixel 8B in place of the phosphor layer.
[0104] The phosphor layer 4 may be formed of only a phosphor
material to be illustrated below, may optionally contain an
additive, or may have a configuration in which such a phosphor
material is dispersed in a binding material, such as a resin
material or an inorganic material. A known phosphor material may be
used as the phosphor material of this embodiment. This kind of
phosphor material may be classified as an organic phosphor material
or an inorganic phosphor material. While specific compounds of
these will be illustrated below, the present embodiment is not
limited to these materials.
[0105] For the organic phosphor material, fluorescent materials for
converting ultraviolet light or blue light into green light may
include, for example, a coumarin-based dye:
2,3,5,6-1H,4H-tetrahydro-8-trifluomethylquinolizine(9,9a,1-gh)coumarin
(coumarin 153), 3-(2'-benzothiazolyl)-7-diethylaminocoumarin
(coumarin 6), 3-(2'-benzimidazolyl)-7-N, and N-diethylaminocoumarin
(coumarin 7), and a naphthalimide-based dye: basic yellow 51,
solvent yellow 11, and solvent yellow 116. In addition, fluorescent
materials for converting ultraviolet light or blue light into red
light may include, for example, a cyanine-based dye:
4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran, a
pyridine-based dye:
1-ethyl-2-[4-(p-dimethylaminophenyl)-1,3-butadienyl]-pyridinium-perchlora-
te, and a rhodamine-based dye: rhodamine B, rhodamine 6G, rhodamine
3B, rhodamine 101, rhodamine 110, basic violet 11, and
sulforhodamine 101.
[0106] For the inorganic phosphor material, fluorescent materials
for converting ultraviolet light or blue light into green light may
include, for example, (BaMg)Al.sub.16O.sub.27:Eu.sup.2+, Mn.sup.2+,
Sr.sub.4Al.sub.14O.sub.25:Eu.sup.2+,
(SrBa)Al.sub.12Si.sub.2O.sub.8:Eu.sup.2+,
(BaMg).sub.2SiO.sub.4:Eu.sup.2+, Y.sub.2SiO.sub.5:Ce.sup.3+,
Tb.sup.3+, Sr.sub.2P.sub.2O.sub.7-Sr.sub.2B.sub.2O.sub.5:Eu.sup.2+,
(BaCaMg).sub.5(PO.sub.4).sub.3Cl:Eu.sup.2+,
Sr.sub.2Si.sub.3O.sub.8-2 SrCl.sub.2:Eu.sup.2+, Zr.sub.2SiO.sub.4,
MgAl.sub.11O.sub.19:Ce.sup.3+, Tb.sup.3+,
Ba.sub.2SiO.sub.4:Eu.sup.2+, Sr.sub.2SiO.sub.4:Eu.sup.2+, and
(BaSr)SiO.sub.4:Eu.sup.2+.
[0107] Further, fluorescent materials for converting ultraviolet
light or blue light into red light may include, for example,
Y.sub.2O.sub.2S:Eu.sup.3+, YAlO.sub.3:Eu.sup.3+,
Ca.sub.2Y.sub.2(SiO.sub.4).sub.6:Eu.sup.3+,
LiY.sub.9(SiO.sub.4).sub.6O.sub.2:Eu.sup.3+, YVO.sub.4:Eu.sup.3+,
CaS:Eu.sup.3+, Gd.sub.2O.sub.3:Eu.sup.3+,
Gd.sub.2O.sub.2S:Eu.sup.3+, Y(P,V)O.sub.4:Eu.sup.3+,
Mg.sub.4GeO.sub.55F:Mn.sup.4+, Mg.sub.4Geo.sub.6:Mn.sup.4+,
K.sub.5Eu.sub.25(WO.sub.4).sub.6.25, Na.sub.5Eu.sub.2
5(WO.sub.4).sub.6.25, K.sub.5Eu.sub.2.5(MoO.sub.4).sub.6.25, and
Na.sub.5Eu.sub.2 5(MoO.sub.4).sub.6.25.
[0108] Further, micronization of a semiconductor material such as
CdSe, ZnSe, InP or S1 to a nanosize for fluorescent emission is
known. Visible light is emitted with a size of about 2 nm to about
8 nm, but an emission wavelength is shorter as a particle size is
smaller.
[0109] The phosphor layer 4 can be formed through a known wet
process by a coating method such as a spin coating method, a
dipping method, a doctor blade method or a spray coat method, or a
printing method such as an ink-jet method, a relief printing
method, an intaglio printing method, or a screen printing method
using a solution in which the phosphor material and the resin
material are dissolved or dispersed in a solvent; a known dry
process such as a resistance heating deposition method, an electron
beam (EB) deposition method, a molecular beam epitaxy (MBE) method,
a sputtering method, or an organic vapor phase deposition (OVPD)
method using the above material; or a laser transfer method.
[0110] Further, the phosphor layer 4 may be patterned by a
photolithography method using a photosensitive resin as the above
resin material. For the photosensitive resin, one kind or a mixture
of a plurality of kinds of photosensitive resins (photo-curable
resist materials) having a reactive vinyl group, such as an
acrylic-acid-based resin, a methacrylic-acid-based resin, or a hard
rubber-based resin. In addition, the phosphor material may also be
directly patterned using a wet process such as the ink jet method,
the relief printing method, the intaglio printing method, or the
screen printing method described above; the known dry process such
as the resistance heating deposition method, the electron beam (EB)
deposition method, the molecular beam epitaxy (MBE) method, the
sputtering method, or the organic vapor phase deposition (OVPD)
method using a mask; or the laser transfer method.
[0111] The low refractive index layer 5 is arranged between the
phosphor layer 4 and the band pass filter 6. The low refractive
index layer 5 is formed as a layer having a refractive index lower
than that of either the phosphor layer or the band pass filter
layer. Specifically, for example, when a refractive index of the
phosphor layer 4 is 1.58 and a refractive index of the band pass
filter 6 is 1.59, an air layer having a refractive index of 1.0 may
be used as the low refractive index layer 5.
[0112] The band pass filter 6 has a structure of a dielectric
multilayer film or the like, and reflects, to the observer, light
emitted to the backlight 10 of a light component fluorescently
emitted within the phosphor layer 4. Particularly, the function of
the band pass filter 6 will be described below. For light at an
incidence angle 0.degree., that is, light incident in parallel to a
panel normal direction from the backlight 10, the band pass filter
6 transmits the light in the blue region and reflects light ranging
from a green region to a near-infrared region.
[0113] Therefore, for example, there is a characteristic that the
blue light having high directivity from the backlight 10 is
transmitted at high transmittance, and the light color-converted
and emitted isotropically within the phosphor layer 4 is reflected
at high reflectance.
[0114] In addition, it is preferable for the band pass filter 6 to
have such a thickness that optical crosstalk exciting a phosphor
installed in a neighboring pixel region does not occur until the
light transmitted through the second polarization plate 27 is
incident on the phosphor layer 4. Specifically, it is preferable
for the thickness of the band pass filter 6 to be smaller than a
distance between pixels.
[0115] (2) Operation and Effects of the Display Element
[0116] Next, operation of the first embodiment in which the low
refractive index layer 5 is arranged between the phosphor layer 4
and the band pass filter 6 will be described with reference to
FIGS. 1 to 4. However, problems of a display element of a
comparative example will first be described with reference to a
drawing.
[0117] In addition, the same components as those in the drawings
used in the first embodiment are denoted with the same reference
signs in the description of the comparative example, and a detailed
description thereof is omitted.
[0118] FIG. 13 is a schematic cross-sectional view illustrating
primary portions of a display element 100 of the comparative
example. In the display element 100, a first polarization plate 21,
a first substrate 22, a liquid crystal layer 24, a second substrate
26, a second polarization plate 27, a band pass filter 6, a
phosphor layer 4, a color filter layer 11, and a substrate 3 are
laminated in this order from a backlight 10 (see FIG. 1) side. The
phosphor layer 4 and the band pass filter 6 are bonded without a
low refractive index layer interposed therebetween. A resin having
substantially the same refractive index as those of the phosphor
layer 4 and the band pass filter 6 is used for bonding.
[0119] Next, an incidence angle dependence of a reflection
characteristic of the band pass filter 6 will be described with
reference to FIGS. 3A and 3B. FIG. 3A shows reflectance due to an
incident angle for each wavelength of incident light, in which a
horizontal axis indicates the wavelength, and a vertical axis
indicates the reflectance. Respective incidence angles
(0.0.degree., 13.0.degree., 19.2.degree., 30.3.degree.,
38.2.degree. and 41.1.degree.) indicate angles within a medium
constituting the band pass filter 6.
[0120] For the light at an incidence angle of 0.0.degree.,
reflectance of the blue light source indicating a maximum light
amount in a blue region, that is, in a range of wavelengths from
410 nm to 480 nm, is about 0%, and the light in this region is
transmitted. For example, a maximum light amount wavelength of the
backlight including a blue LED in the light source is 455 nm, and
the light is transmitted by the band pass filter 6.
[0121] On the other hand, when the incidence angle is 0.degree.,
light ranging from a green region to a near-infrared region, that
is, a region of wavelengths from 500 nm to 1000 nm, is reflected by
about 100%, but a reflection spectrum shifts to a short wavelength
side as the incidence angle increases. For example, if the
incidence angle is 41.1.degree., light in a region of longer
wavelengths than a wavelength of 700 nm is hard to reflect (see
FIG. 3A).
[0122] In other words, the band pass filter 6 has a characteristic
that the band pass filter 6 transmits the blue light having high
directivity from the backlight 10 at high transmittance and
reflects the light color-converted and emitted isotropically within
the phosphor layer at high reflectance. Such a characteristic of
the band pass filter 6 is called a blue shift characteristic in the
following description.
[0123] FIG. 3B schematically illustrates a reflection
characteristic according to an angle of incidence on the band pass
filter 6 of the light excited in the phosphor layer.
[0124] The light color-converted in the phosphor layer 4 and
incident on the band pass filter 6 is isotropic, and an incidence
angle thereof ranges from 0.degree. to a maximum of 90.degree..
However, a light component at an incidence angle .alpha. less than
.+-.42.degree. with respect to a panel normal N-N is reflected in
the band pass filter 6 and reflected from the substrate 3 to the
outside, that is, toward an observer, due to the blue shift
characteristic of the band pass filter. On the other hand, a light
component incident on the band pass filter 6 at an incidence angle
.beta. exceeding .+-.142.degree. with respect to the panel normal
N-N, which is a light component in a long wavelength region, i.e.,
a red region, cannot be reflected to the observer (see FIG.
3B).
[0125] Dependence of an angle of incidence on the band pass filter
6 of the reflection spectrum is illustrated in FIGS. 14A and
14B.
[0126] FIG. 14A is a graph showing a relationship between
transmittance and reflectance, and an incidence wavelength when an
angle of incidence on the band pass filter 6 is 0.degree., i.e., at
the time of normal incidence. Further, FIG. 14B is a graph showing
a relationship between transmittance and reflectance, and an
incidence wavelength when an angle of incidence on the band pass
filter 6 is 39.degree., i.e., a maximum incidence angle. According
to these graphs, when an angle of the light incident on the band
pass filter 6 is inclined from a vertical direction to a horizontal
direction, decrease in transmittance and increase in reflectance on
the long wavelength side shift to a short wavelength. In addition,
it is seen that increase in transmittance and decrease in
reflectance occur in a central wavelength region.
[0127] When the band pass filter 6 is formed of a dielectric
multilayer film, influence of the blue shift characteristic is
strong, as described above. Accordingly, in order to reflect an
entire visible light region in the light in the range of all
incidence angles, i.e., 0.degree. to 90.degree., it is necessary
for the light at all the incidence angles to satisfy a condition of
2ndsin.theta.=m.lamda. when the incidence angle is .theta., a
refractive index of the dielectric multilayer film is n, and a film
thickness of one layer of a repetition unit of the high refractive
index layer and the low refractive index layer is d.
[0128] For example, when light at a wavelength of 650 nm is
incident on the band pass filter 6 and this light is reflected, the
light can be reflected when the film thickness of one layer of the
dielectric multilayer film is about 205 nm at the incidence angle
of 0.degree.. On the other hand, it is necessary for the one layer
of the dielectric multilayer film to have a film thickness of 411
nm at the incidence angle of 60.degree. and a film thickness of
1184 nm at the incidence angle of 80.degree.. The dielectric
multilayer film may include tens of layers to 100 layers or more
and the layer thickness of the band pass filter 6 becomes
excessively great.
[0129] When the band pass filter 6 having such a layer thickness is
arranged between the phosphor layer and the liquid crystal layer,
optical crosstalk in which a phosphor installed in an adjacent
pixel region is excited before the light transmitting the second
polarization plate is incident on the phosphor layer occurs.
[0130] FIG. 2 is a schematic cross-sectional view illustrating
primary portions of the first embodiment. The first polarization
plate 21, the first substrate 22, the liquid crystal layer 24, the
second substrate 26, the second polarization plate 27, the band
pass filter 6, the low refractive index layer 5, the phosphor layer
4, the color filter layer 11, and the substrate 3 are laminated in
this order from the backlight 10 (see FIG. 1) side. A light
extraction structure 9 is arranged between the substrate 3 and the
band pass filter 6 for each pixel. In other words, the display
element 1 of the first embodiment is different from the display
element 100 according to the comparative example in that the low
refractive index layer 5 is arranged between the phosphor layer 4
and the band pass filter 6.
[0131] For example, a component at an incidence angle .alpha.
smaller than +39.degree. with respect to a panel normal N-N in the
light on the backlight 10 side emitted isotropically within the
phosphor layer 4 having a refractive index of 1.58 is transmitted
through the low refractive index layer 5 and incident on the band
pass filter 6, but since the blue shift characteristic is given to
a reflection band of the band pass filter 6, light ranging from a
green region to a red region is reflected by the band pass filter 6
and returned to the phosphor layer 4 again, as illustrated in FIG.
4. Since the light extraction structure 9 is arranged in the same
layer of the phosphor layer 4, a light path of the light returned
to the phosphor layer 4 may be changed due to the reflection and
the light can be emitted to the outside, that is, the observer
side.
[0132] On the other hand, when light of a component at an incidence
angle .beta. greater than .+-.39.degree. with respect to a panel
normal N-N is incident on the low refractive index layer 5, the
light is totally reflected, scattered by the light extraction
structure 9 or a scatterer in the color filter 11, and emitted to
the outside, that is, the observer side. Therefore, according to
the display element of this embodiment, it is possible to
efficiently extract the excitation light emitted isotropically
within the phosphor layer 4 toward the observer.
[0133] In addition, in the display element 1 of this embodiment,
only the component at an incidence angle .alpha. smaller than
.+-.39.degree. with respect to a panel normal N-N in the light
incident on the low refractive index layer 5 formed of an air layer
(refractive index: 1.0) is incident on the band pass filter 6.
Accordingly, the band pass filter 6 is formed of a functional
optical film having a layer thickness at which the optical
crosstalk does not occur, and specifically a total film thickness
of about 100 .mu.m, such that the band pass filter 6 capable of
reflecting an entire wavelength region can be formed.
[0134] It is preferable for the reflection band of the band pass
filter of this embodiment to be set to include an emission spectrum
of a red phosphor and an emission spectrum of a green phosphor.
When the blue shift of the band pass filter is considered, it is
preferable for a reflection band for the light at a maximum
incidence angle incident on the band pass filter to sufficiently
include the emission spectrum of the red phosphor.
[0135] When a refractive index n of the medium is n, the incidence
angle is .theta., and a reflection wavelength at the incidence
angle 0.degree. is .lamda.0, the blue shift of the band pass filter
has a relationship of
.lamda.(.theta.)=.lamda.0.times.cos(sin-1(sin(.alpha.)/n).
Accordingly, it is necessary for a long wavelength end of the
reflection band at the incidence angle 0.degree. to be about 1000
nm in order for the long wavelength end of the reflection band of
the band pass filter to include 750 nm that is a long wavelength
end of the emission spectrum of the red phosphor when the incidence
angle .alpha. is a maximum incidence angle 39.degree. under the
above conditions.
[0136] In addition, since the reflection band of the band pass
filter as described above can be appropriately designed according
to the refractive index of the material used and an emission
spectrum of a light emitting body, the reflection band is not
limited to the values described above.
[0137] (3) A Laminating Method for the Display Element
[0138] A bonding method for the display element 1 will be described
with reference to FIGS. 5A to 6C.
[0139] FIG. 5A is a schematic cross-sectional view illustrating a
method of bonding the primary portions of the display element 1 of
this embodiment. FIG. 5B is a cross-sectional view illustrating a
bonded configuration of the primary portions of the display element
1 of this embodiment.
[0140] A lower substrate 200 in which the liquid crystal panel 20
with the liquid crystal layer 24 interposed between the first
substrate 22 including the first polarization plate 21 on the
backlight 10 side and the second substrate 26 including the second
polarization plate 27 on the observer side is used as a support,
and the band pass filter 6 is formed on the observer side, and an
upper substrate 300 in which the substrate 3 including the color
filter layer 11 and the phosphor layer 4 formed thereon is used as
a support are bonded through an air layer. In addition, the air
layer may be an inert gas such as dry air, nitrogen and argon, as
well as atmospheric air (see FIG. 5A).
[0141] The light extraction structure 9 for defining the subpixels
8R, 8G and 8B as regions is formed in the upper substrate 300. The
light extraction structure 9 is a structure formed of a white
scatterer such as a resin in which titanium oxide is dispersed, and
diffusively reflects a part of light emitted by the phosphor layer
4 to increase efficiency of light extraction toward the observer.
In addition, the light extraction structure 9 may be a reflective
material in which fine metal particles are dispersed or may be a
reflective material on a surface of which a metal film is
deposited.
[0142] The light extraction structure 9 is formed to protrude at
least 1 .mu.m or more from the band pass filter 6 side of the
phosphor layer 4. When the upper substrate 300 is bonded to the
lower substrate 200, the protruding portion of the light extraction
structure 9 functions as a spacer for maintaining a constant gap
between the substrates and holding the low refractive index layer 5
(an air layer) therein.
[0143] A schematic cross-sectional view of the primary portions of
the display element of this embodiment bonded using such a method
is illustrated in FIG. 5B.
[0144] It is necessary to pattern the light extraction structure 9
before forming the color filter layer 11 and the phosphor layer 4.
Therefore, it may be difficult to give an adhesive property to the
light extraction structure 9 from the viewpoint of production
efficiency, and adhesion to a peripheral portion of the display
area may be performed using, for example, a peripheral sealing
material S1 such as an epoxy based adhesive or an acrylic based
adhesive.
[0145] The peripheral sealing material S1 may be provided
continuously in the outer peripheral portion of the panel as
illustrated in FIG. 6A, but there is a possibility of a change in
volume of the air layer being caused and the sealing portion
causing peeling due to change in atmospheric pressure or
temperature when the upper substrate 300 and the lower substrate
200 are bonded as a complete sealing structure. Therefore, it is
preferable to provide an opening as a vent in a portion of the
peripheral sealing material S1 (see FIG. 6B).
[0146] In addition, the peripheral sealing material S1 may be
appropriately selectively provided in corner portions or portions
of respective sides of the outer periphery of the panel, as
illustrated in FIG. 6C.
[0147] In this embodiment, the light extraction structure 9 can
uniformly hold a gap of the low refractive index layer 5 since the
light extraction structure 9 is arranged in each pixel and has a
function of a spacer between the phosphor layer 4 and the band pass
filter 6.
[0148] (4) Variant
[0149] A variant of the display element according to this
embodiment is illustrated in FIG. 7. The display element 1A of this
variant is formed in such a manner that the protruding portion of
the light extraction structure 9 has an adhesive layer 9c. The
upper substrate 300 including such a light extraction structure 9
is directly bonded to the lower substrate 200 through the light
extraction structure 9, such that the gap of the low refractive
index layer 5 can be uniformly held.
[0150] In addition, the substrates may be bonded by additionally
using the peripheral sealing material S1 for the purpose of further
improving adhesive strength. Further, such a peripheral sealing
material S1 may be provided continuously in the outer peripheral
portion of the panel or may be provided appropriately selectively
in corner portions or portions of respective sides of the panel
periphery (see FIGS. 6A to 6C).
Second Embodiment
[0151] Hereinafter, a display element 1B of a second embodiment of
the present invention will be described using FIGS. 8A and 8B.
[0152] A basic configuration of the display element 1B of this
embodiment is the same as that of the display element 1 of the
first embodiment, and the second embodiment is different from the
first embodiment in that glass surfaces of an upper substrate 300
and a lower substrate 200 are directly bonded by a peripheral
sealing material S2.
[0153] FIG. 8A is a schematic cross-sectional view illustrating a
method of bonding primary portions of the display element 1B of
this embodiment. FIG. 8B is a cross-sectional view illustrating a
bonded configuration of the primary portions of the display element
1B of this embodiment. The same components in FIGS. 8A and 8B as
those in FIG. 1 of the first embodiment are denoted with the same
reference signs and a detailed description thereof is omitted.
[0154] (1) Configuration of the Display Element
[0155] In the display element 1B of the second embodiment, a first
polarization plate 21, a first substrate 22, a liquid crystal layer
24, a second substrate 26, a second polarization plate 27, a band
pass filter 6, a low refractive index layer 5, a phosphor layer 4,
a color filter layer 11, and a substrate 3 are laminated in this
order from the backlight 10 (see FIG. 1) side.
[0156] A light extraction structure 9, the color filter layer 11,
and the phosphor layer 4 are formed on the substrate 3. The first
substrate 21 and the second substrate 26 are bonded with the liquid
crystal layer 24 interposed therebetween.
[0157] The polarization plate 27 and the band pass filter 6 are
arranged on one surface on the observer side of the second
substrate 26 through a bonding layer (adhesive layer), and the
substrate 3 on which the light extraction structure 9, the color
filter layer 11, and the phosphor layer 4 are formed is bonded
through an air layer as the low refractive index layer 5 (see FIG.
8B).
[0158] The display element 1B of this embodiment is configured in
such a manner that a lower substrate 200 in which the liquid
crystal panel 20 with the liquid crystal layer 24 interposed
between the first substrate 22 including the first polarization
plate 21 on the backlight 10 side and the second substrate 26
including the second polarization plate 27 on the observer side is
used as a support, and the band pass filter 6 is formed on the
observer side, and an upper substrate 300 in which the substrate 3
including the color filter layer 11 and the phosphor layer 4 formed
thereon is used as a support, i.e., glass surfaces of the upper
substrate 300 and the lower substrate 200 are directly bonded by
the peripheral sealing material S2. A uniform gap is held between
the phosphor layer 4 and the band pass filter 6 using the light
extraction structure 9 as a spacer and the low refractive index
layer 5 is formed (see FIG. 8A).
[0159] Further, in order to prevent peripheral portions of, for
example, the color filter layer 11, the phosphor layer 4, the
polarization plate 27 and the band pass filter 6 from coming in
contact or interfering with the peripheral sealing material S2, it
is preferable to provide a certain gap K in a border portion
between the peripheral sealing material S2 and, for example, the
color filter layer 11, the phosphor layer 4, the polarization plate
27 and the band pass filter 6 (see FIG. 8B).
[0160] (2) Operation and Effects of the Display Element
[0161] However, the color filter layer 11 or the phosphor layer 4
constituting the upper substrate 300 and the polarization plate 27
or the band pass filter 6 constituting the lower substrate 200 are
both formed of organic films. Particularly, since the polarization
plate 27 or the band pass filter 6 is formed by laminating a
bonding layer, an adhesive layer, or a resin layer such as a PET
(polyethylene terephthalate) base or a PVA (polyvinyl alcohol)
film, the polarization plate 27 or the band pass filter 6 has a
different linear expansion coefficient from the glass substrate.
When the peripheral sealing material is adhered to these organic
films, there is a possibility of warpage or positional displacement
occurring in the substrate due to shrinkage of the organic
film.
[0162] Since the display element 1B according to this embodiment
has a configuration in which the glass surfaces of the substrates
are directly adhered by the peripheral sealing material S2 on the
outer side of these organic films, it is possible to prevent
warpage or positional displacement of the substrate from occurring
due to the shrinkage of the organic film.
[0163] According to the display element 1B of this embodiment, the
low refractive index layer 5 is arranged between the phosphor layer
4 and the band pass filter 6. Accordingly, if light on the
backlight 10 side emitted isotropically within the phosphor layer 4
is incident on the low refractive index layer 5, the light is
totally reflected, scattered by the light extraction structure 9 or
a scatterer in the color filter 11, and emitted to the outside,
that is, an observer side.
[0164] Therefore, according to the display element of this
embodiment, it is possible to efficiently extract the excitation
light emitted isotropically within the phosphor layer 4 toward the
observer.
Third Embodiment
[0165] Hereinafter, a display element 1C of a third embodiment of
the present invention will be described using FIG. 9.
[0166] A basic configuration of the display element 1C of this
embodiment is the same as that of the display element 1 of the
first embodiment, and the third embodiment is different from the
first embodiment in that a low refractive index resin layer 12 is
arranged between a phosphor layer 4 and a band pass filter 6
instead of the air layer.
[0167] FIG. 9 is a schematic cross-sectional view illustrating
primary portions of the display element 1C of this embodiment. The
same components in FIG. 9 as those in FIG. 1 of the first
embodiment are denoted with the same reference signs and a detailed
description thereof is omitted.
[0168] In the display element 1C of this embodiment, the low
refractive index resin layer 12 is arranged between the phosphor
layer 4 and the band pass filter 6, as illustrated in FIG. 9. For
the low refractive index resin layer 12, for example, a porous film
such as nanoporous silica or mesoporous silica, which is a material
having a smaller refractive index than the phosphor layer 4 or the
band pass filter 6, or a fluorine-based resin may be used. For
example, mesoporous silica (Sumitomo Osaka Cement Co., Ltd.) and
Mesoporous (Nippon Kasei Chemical Co., Ltd.) have a refractive
index of about 1.18 to about 1.27, which is smaller than the
refractive index of the phosphor layer 4 or the band pass filter 6,
and are suitable as the low refractive index resin layer 12. For
the fluorine-based resin, for example, Cytop (Asahi Glass
Corporation) has a refractive index 1.34 and is similarly suitable
as the low refractive index resin layer 12.
[0169] In addition, a porous silicon film may be formed by a
sol-gel reaction using a reactive alkoxy silane as a starting raw
material.
[0170] (2) Operation and Effects of the Display Element
[0171] According to the display element 1C of this embodiment, the
low refractive index resin layer 12 formed of a medium having a
smaller refractive index than the phosphor layer 4 or the band pass
filter 6 is arranged between the phosphor layer 4 and the band pass
filter 6. Accordingly, when light on the backlight 10 side emitted
isotropically within the phosphor layer 4 is incident on the low
refractive index resin layer 12, the light is totally reflected,
scattered by the light extraction structure 9 or a scatterer in the
color filter 11, and emitted to the outside, that is, an observer
side.
[0172] Therefore, according to the display element of this
embodiment, it is possible to efficiently extract the excitation
light emitted isotropically within the phosphor layer 4 toward the
observer.
Variant of the Third Embodiment
[0173] FIG. 15 is a cross-sectional view illustrating a variant of
the display element of the third embodiment.
[0174] According to a display element 1F of this embodiment, a band
pass filter 36 includes two layers including a low refractive index
layer 36A and a dielectric multilayer film 3613. Also, an adhesive
layer 37 is formed between the band pass filter 36, which includes
the two layers, and a phosphor layer 4, which are bonded to each
other.
[0175] In this embodiment, the band pass filter 36 is formed of a
multilayer stretched film that is an organic material. In film
multi-layering and stretching processes, a constituent material for
the low refractive index layer 36A may be put into the outermost
surface on one side to form a film, in addition to a high
refractive index resin (PEN) and a low refractive index resin (PET)
used for the dielectric multilayer film 36B.
[0176] In addition, in order to secure strength of such a film, it
is also preferable for the outermost surface to be a PEN film
layer, and to provide the low refractive index layer in an
intermediate layer. For example, a fluorine-based polymer resin, or
a polymer in which fine particles having a low refractive index are
dispersed may be used as the material of the low refractive index
layer 36A.
[0177] It is necessary for the low refractive index layer 36A to be
formed to a sufficient thickness not to be involved in optical
interference. For example, it is necessary for the thickness of the
low refractive index layer 36A to be sufficiently greater than a
wavelength region of a visible ray that ranges from 380 nm to 780
nm. Preferably, the thickness of the low refractive index layer 36A
is 1 micron or more. According to such a configuration, it is not
necessary for the adhesive layer of the phosphor layer 4 to have a
low refractive index, and even when a normal adhesive layer is used
for bonding, the low refractive index layer 36A installed in a
portion (the outermost surface or the intermediate layer) of the
band pass filter totally reflects an oblique fluorescent component,
contributing to improvement of the light extraction efficiency.
Therefore, it is possible to expect the same effects as those of
the display element 1C of the third embodiment illustrated in FIG.
9.
Fourth Embodiment
[0178] Hereinafter, a display element 1D of a fourth embodiment of
the present invention will be described using FIG. 10.
[0179] A basic configuration of the display element 1D of this
embodiment is the same as that of the display element 1 of the
first embodiment, and the fourth embodiment is different from the
first embodiment in that a substrate includes a first substrate 22
and a second substrate 26, and a band pass filter 6 and a
polarization plate 27 are arranged in a liquid crystal panel.
[0180] FIG. 10 is a schematic cross-sectional view illustrating
primary portions of the display element 1D of this embodiment. The
same components in FIG. 10 as those in FIG. 1 of the first
embodiment are denoted with the same reference signs and a detailed
description thereof is omitted.
[0181] (1) Configuration of the Display Element
[0182] In the display element 1D of this embodiment, a first
polarization plate 21, a first substrate 22, a liquid crystal layer
24, a second polarization plate 27, a band pass filter 6, a low
refractive index layer 5, a phosphor layer 4, a color filter layer
11, and a second substrate 26 are laminated in this order from the
backlight 10 (see FIG. 1) side, as illustrated in FIG. 10.
[0183] A light extraction structure 9, the color filter layer 11,
and the phosphor layer 4 are laminated on the second substrate 26.
The band pass filter 6 and the second polarization plate 27 are
laminated on the first substrate 22 through a peripheral sealing
material S1 and the low refractive index layer 5. In addition, a
transparent electrode for liquid crystal driving or a light
distribution film is arranged on the liquid crystal layer 24 side
of the second polarization plate (not illustrated). Further, while
an example of the light extraction structure 9 including an
adhesive layer 9c to the band pass filter 6 in a protruding portion
in the display element 1D illustrated in FIG. 10 is shown, the
light extraction structure 9 is not limited thereto.
[0184] The first substrate 22, and the second substrate 26 on which
the light extraction structure 9, the color filter layer 11 and the
phosphor layer 4 are laminated are bonded through the liquid
crystal layer 24 and sealed by a sealing material SC for a liquid
crystal, such that a liquid crystal display element can be
formed.
[0185] (2) Operation and Effects of the Display Element
[0186] According to the display element 1D of this embodiment, the
low refractive index layer 5 is arranged between the phosphor layer
4 and the band pass filter 6. Accordingly, when the light on the
backlight 10 side emitted isotropically within the phosphor layer 4
is incident on the low refractive index layer 5, the light is
totally reflected, scattered by the light extraction structure 9 or
a scatterer in the color filter 11, and emitted to the outside,
that is, an observer side.
[0187] Therefore, according to the display element of this
embodiment, it is possible to efficiently extract the excitation
light emitted isotropically within the phosphor layer 4 toward the
observer.
[0188] In addition, since the display element 1D of this embodiment
has a so-called in-cell structure in which only two surfaces
including the first substrate 22 and the second substrate 26 are
used as a substrate, and the band pass filter 6 and the second
polarization plate 27 are arranged within a liquid crystal cell, it
is possible to suppress increase in thickness of the entire device.
Further, it is possible to suppress increase in weight.
Fifth Embodiment
[0189] Hereinafter, a display element 1E of a fifth embodiment of
the present invention will be described using FIG. 11.
[0190] A basic configuration of the display element 1E of this
embodiment is the same as that of the display element 1 of the
first embodiment. This embodiment is different from the first
embodiment in that a substrate includes only a first substrate 22
and a second substrate 26, a band pass filter 6 and a polarization
plate 27 are arranged within a liquid crystal panel, and a
peripheral sealing material is bonded to glass surfaces of the
first substrate 22 and the second substrate 26.
[0191] FIG. 11 is a cross-sectional view illustrating primary
portions of the display element 1E of this embodiment. The same
components in FIG. 11 as those in FIG. 1 of the first embodiment
are denoted with the same reference signs and a detailed
description thereof is omitted.
[0192] (1) Configuration of the Display Element
[0193] The display element 1E of this embodiment includes a first
polarization plate 21, the first substrate 22, a liquid crystal
layer 24, the second polarization plate 27, the band pass filter 6,
a low refractive index layer 5, a phosphor layer 4, a color filter
layer 11, and the second substrate 26 laminated in this order from
a backlight 10 (see FIG. 1) side, as illustrated in FIG. 11.
[0194] A light extraction structure 9, the color filter layer 11,
and the phosphor layer 4 are laminated on the second substrate 26.
The band pass filter 6 and the second polarization plate 27 are
laminated on the first substrate 21 through the peripheral sealing
material S1 and the low refractive index layer 5. In addition, for
example, a transparent electrode for liquid crystal driving or a
light distribution film is arranged on the liquid crystal layer
side of the second polarization plate (not illustrated). In
addition, the display element 1E illustrated in FIG. 11 shows an
example of the light extraction structure 9 in which an adhesive
layer 9c of the band pass filter 6 is included in a protruding
portion, but the light extraction structure 9 is not limited
thereto.
[0195] In the display element 1E of this embodiment, the glass
surfaces of the second substrate 26 on which the light extraction
structure 9, the color filter layer 11, and the phosphor layer 4
are laminated and the first substrate 22 on which the band pass
filter 6 and the second polarization plate 27 are laminated through
the peripheral sealing material and the low refractive index layer
5 are bonded directly by the peripheral sealing material S2.
[0196] In addition, a sealing portion of the liquid crystal layer
24 and a portion between the phosphor layer 4 and the band pass
filter 6 can be sealed using respective dedicated sealing
materials.
[0197] Further, in the display element 1E of this embodiment, the
color filter layer 11, the phosphor layer 4, the low refractive
index layer 5, the band pass filter 6 and the second polarization
plate 27 are laminated in a space between the first substrate 22
and the second substrate 26, and a gap between the first substrate
22 and the second substrate 26 is large relative to a layer
thickness of the liquid crystal layer 24. Therefore, it is possible
to prevent an outflow of the liquid crystal material using a
dedicated sealing material for the liquid crystal layer.
[0198] In order to prevent peripheral portions of, for example, the
color filter layer 11, the phosphor layer 4, the polarization plate
27 and the band pass filter 6 from coming in contact or interfering
with the peripheral sealing material S2, a certain gap K can be
provided in a border portion between the peripheral sealing
material S2 and, for example, the color filter layer 11, the
phosphor layer 4, the polarization plate 27 and the band pass
filter 6.
[0199] (2) Operation and Effects of the Display Element
[0200] However, the color filter layer 11 or the phosphor layer 4
laminated on the second substrate 26 and the polarization plate 27
or the band pass filter 6 laminated on the first substrate 22 are
both formed of organic films. Particularly, since the polarization
plate 27 or the band pass filter 6 is formed by laminating a
bonding layer, an adhesive layer, or a resin layer such as a PET
(polyethylene terephthalate) base or a PVA (polyvinyl alcohol)
film, the polarization plate 27 or the band pass filter 6 has a
different linear expansion coefficient from a glass substrate. When
the peripheral sealing material S2 is adhered to these organic
films, there is a possibility of warpage or positional displacement
occurring in the substrate due to shrinkage of the organic
film.
[0201] Since the display element IE according to this embodiment
has a configuration in which the glass surfaces of the first
substrate 22 and the second substrate 26 are directly adhered by
the peripheral sealing material S2 on the outer side of these
organic films, it is possible to prevent warpage or positional
displacement of the substrate from occurring due to the shrinkage
of the organic film.
[0202] According to the display element 1E of this embodiment, the
low refractive index layer 5 is arranged between the phosphor layer
4 and the band pass filter 6. Accordingly, if light on the
backlight 10 side emitted isotropically within the phosphor layer 4
is incident on the low refractive index layer 5, the light is
totally reflected, scattered by the light extraction structure 9 or
a scatterer in the color filter 11, and emitted to the outside,
that is, an observer side.
[0203] Therefore, according to the display element of this
embodiment, it is possible to efficiently extract the excitation
light emitted isotropically within the phosphor layer 4 toward the
observer.
[0204] In addition, while the example in which the light extraction
structure 9 is formed to protrude at least 1 .mu.m or more from the
band pass filter 6 side of the phosphor layer 4 so that a gap
between the phosphor layer 4 and the band pass filter 6 is
maintained constant, and functions as a spacer holding the low
refractive index layer 5 (air layer) therein has been described in
each embodiment described above, one end of the light extraction
structure 9 may be formed to be coplanar with one surface on the
band pass filter 6 side of the phosphor layer 4, and the gap of the
low refractive index layer 5 may be maintained constant by
arranging another spacer. Specifically, a phosphor may be dropped
into the light extraction structure subjected to hydrophilic
treatment and water-repellent treatment, and patterning may be
performed using a difference in wettability.
[0205] It is possible to bond the phosphor layer 4 and the band
pass filter 6 in parallel with higher precision by bonding them
using such a method.
[0206] Further, while the configuration in which the backlight 10
and the liquid crystal panel 20 are included as the optical
modulation portion 2 has been described in each embodiment
described above, the present invention is not limited thereto. For
example, a blue light emitting EL element 2A may be used as the
optical modulation portion, as illustrated in FIG. 12.
[0207] For the blue light emitting EL element 2A used in this
embodiment, a known organic EL may be used. The blue light emitting
EL element 2A, for example, is a light emitting element having a
configuration in which an anode 41, a hole injection layer 43, a
hole transport layer 44, a light emitting layer 45, a hole blocking
layer 46, an electron transport layer 47, an electron injection
layer 48, and a cathode 49 are sequentially laminated on one
surface of the substrate 40. An edge cover 42 is formed to cover
the end surface of the anode 41. The blue light emitting EL element
2A may include an organic EL layer that includes a light emitting
layer (an organic light emitting layer) 45 formed of at least an
organic light emitting material between the anode 41 and the
cathode 49, and a specific configuration thereof is not limited to
the above configuration.
[0208] The blue light emitting EL element 2A is provided in a
matrix form to correspond to each of the subpixels 8R, 8G and 8B
illustrated in FIG. 1, and is adapted to be individually turned
on/off. A method of driving the blue light emitting EL element 2A
may be an active matrix driving method or may be a passive matrix
driving method.
[0209] The blue light emitting EL element 2A is electrically
connected to an external driving circuit. In this case, the blue
light emitting EL element 2A may be directly connected to and
driven by the external driving circuit, or a switching circuit such
as a TFT may be arranged in a pixel and an external driving circuit
(a scanning line electrode circuit (source driver), a data signal
electrode circuit (gate driver), and a power supply circuit) may be
electrically connected to a wiring to which, for example, the TFT
is connected.
[0210] Further, while the case in which the blue light emitting EL
element is the blue light emitting organic EL element has been
described in this embodiment, the blue light emitting EL element
may be a blue light emitting inorganic EL element.
[0211] Further, while the blue light emitting EL element has been
illustrated as the optical modulation portion in this embodiment,
the present invention is not limited thereto and an ultraviolet
light emitting EL element (ultraviolet light emitting organic EL
element or an ultraviolet light emitting inorganic EL element) may
be used.
[0212] Further, while the configuration including the light source
and the liquid crystal element, and the blue light emitting EL
element have been illustrated as the optical modulation portion in
the embodiments described above, for example, an MEMS (Micro
Electro Mechanical Systems) display may be used instead. In
addition, an optical switch device such as a digital mirror device
(DMD) may also be used.
[0213] One embodiment of an illumination device including the
display element as described above is shown below.
[0214] FIGS. 16A and 16B are cross-sectional views illustrating one
embodiment of an illumination device. This illumination device 500
includes the display element 1 illustrated in FIG. 1. In other
words, the illumination device 500 includes a phosphor layer 4, a
band pass filter 6, and a low refractive index layer 5 arranged
between the phosphor layer 4 and the band pass filter 6. Further,
the illumination device 500 includes a backlight (light source) 10
that is a light source.
[0215] The backlight (light source) 10 has a configuration in which
light of a light emitting body 10a provided in one end is spread in
a surface shape by a light guide body 10b, as illustrated in FIG.
16A, or a backlight (light source) 10 that is a surface light
emitting body may be used, as illustrated in FIG. 16B. The
backlight (light source) 10 may be, for example, a blue light
source. For the backlight (light source) 10, a blue light emitting
organic EL light emitting body may be used. For example, when an
active matrix organic EL light emitting body is used, a surface
light source of area light control can be obtained. In addition,
the surface light source of area light control can be obtained even
when a liquid crystal element is used. Also, it is possible to
improve light extraction efficiency by using the low refractive
index layer 5 between the phosphor 4 and the band pass filter 6.
For the phosphor 4, a phosphor (e.g., YAG) that converts a blue
light source into white may be used, and a desired color such as
red or green can also be developed.
INDUSTRIAL APPLICABILITY
[0216] The present invention is applicable in the field of display
elements.
REFERENCE SYMBOLS
[0217] 1, 1A, 1B, 1C, 1D, 1E . . . display element, [0218] 2 . . .
optical modulation portion, [0219] 2A . . . blue light emitting EL
element, [0220] 3, 22, 26, 40 . . . substrate, [0221] 4 . . .
phosphor layer, [0222] 5 . . . low refractive index layer, [0223] 6
. . . band pass filter, [0224] 9 . . . light extraction structure,
[0225] 10 . . . backlight (light source), [0226] 11 . . . color
filter layer, [0227] 12 . . . low refractive index resin layer,
[0228] 20 . . . liquid crystal panel (optical modulation element),
[0229] 21 . . . first polarization plate, [0230] 24 . . . liquid
crystal layer, [0231] 27 . . . second polarization plate, [0232]
S1, S2 . . . peripheral sealing material, [0233] SC . . . liquid
crystal sealing material
* * * * *